Customers SSNO PK name addr phone 1..1 0..* PK Bookings row seat PK 0..* 1..1 Flights number PK day PK aircraft Figure 4.43: A UML diagram analogous to the E/R diagram of Fig. 4.29 4.8.5 Exercises for Section 4.8 Exercise 4.8.1: Convert the UML diagram of Fig. 4.43 to relations.

Determine which of these relations are reflexive. The variables x,y,x',y' represent integers. A. x~y if and only if x+y is even B. x~y if and only if x+y is odd C. x~y if and only if x+y is positive D. x~y if and only if xy is positive E. x~y if and only if x-y is a multiple of 10

Electrical connectivity is an example of equivalence relation.a) trueb) false

39 of 40 Let R = (A, B, C, D) be a relation schema with the FD's: A → B and B → A. R has how many superkeys? (Write your answer as an integer). write your answer here